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New DIY Altoids Tin Amp - The Class A "Wintergreen Handwarmer" by xrk971 - Page 2

post #16 of 161
Quote:
Originally Posted by stellarelephant View Post


I've signed up for two boards. Assuming that I'm successful with both builds, I'll have a loaner on hand!

 

Excellent, I'd love to get word out about this little gem. I love these sort of projects.  Keep in touch!

post #17 of 161
Thread Starter 

Yeah, I think this amp could make quite a splash, if it sounds anywhere near as good as the designer has made it out to be. 22 folks are going in on the initial GB, so that's promising.

 

Ike1985, It looks like your IEMs are 16 ohms.  I *think* that this amp will give decent bass with a headphone impedance that low, but it may be less sub bass than you are used to.  X originally designed it to match his 250 ohm Beyerdynamic DT880s, and then he modified the deisign to pair well with most over-ear headphones.  Using the 390 uF output capacitors X is now recommending for the build, bass response will be essentially be very flat down to 20 Hz with any headphone of 50 Ohms or more.  With your IEM's there will probably be a little bit of low-end roll-off due to not quite meeting NvAvGuy's famous "1/8 rule" for impedance matching.  There is a way to predict the bass roll-off, which I just learned how to use!  Oh boy, lets do some math!

 

I learned this from DIYA guru AndrewT, who posted this prediction for the Wintergreen amp with another user's 70 ohm cans, along with his formula here:

 http://www.diyaudio.com/forums/group-buys/302859-xrk971-pocket-class-headamp-gb-3.html

Quote:

"It's a passive single pole filter. Calculate the F-3dB

It will have virtually no roll off @ 60Hz and probably no more than about -0.5dB @ 20Hz 
F-3dB = 1 / 2PiRC = ~6Hz "
 
R is the headphone impedance in Ohms and C is the capacitor value in Farads (which is 0.00039390F aka 390uF in this amp).  
 
So for your 16 ohm IEMs...
F-3dB = 1 / 2Pi(16 ohms)(0.00039F) = ~26 Hz
 
If you'd rather cheat, here is an online calculator that does it for you...
 
-3dB at 26 Hz would be subtle but possibly audible, especially in the sub bass, at least.  Do you have any other cans to listen with?  I also may inquire at DIYA about using a larger output cap to pair better with sensitive headphones, although I'm not sure how big a cap will fit or whether if it may have any effect on sound quality in other ways.

 

The ALO CDM looks insanely nice...did you part ways with yours?  How hot did that thing get?


Edited by stellarelephant - 2/3/17 at 9:11pm
post #18 of 161
Quote:
Originally Posted by stellarelephant View Post
 

Yeah, I think this amp could make quite a splash, if it sounds anywhere near as good as the designer has made it out to be. 22 folks are going in on the initial GB, so that's promising.

 

Ike1985, It looks like your IEMs are 16 ohms.  I *think* that this amp will give decent bass with a headphone impedance that low, but it may be less sub bass than you are used to.  X originally designed it to match his 250 ohm Beyerdynamic DT880s, and then he modified the deisign to pair well with most over-ear headphones.  Using the 390 uF output capacitors X is now recommending for the build, bass response will be essentially be very flat down to 20 Hz with any headphone of 50 Ohms or more.  With your IEM's there will probably be a little bit of low-end roll-off due to not quite meeting NvAvGuy's famous "1/8 rule" for impedance matching.  There is a way to predict the bass roll-off, which I just learned how to use!  Oh boy, lets do some math!

 

I learned this from DIYA guru AndrewT, who posted this prediction for the Wintergreen amp with another user's 70 ohm cans, along with his formula here:

 http://www.diyaudio.com/forums/group-buys/302859-xrk971-pocket-class-headamp-gb-3.html

Quote:

"It's a passive single pole filter. Calculate the F-3dB

It will have virtually no roll off @ 60Hz and probably no more than about -0.5dB @ 20Hz 
F-3dB = 1 / 2PiRC = ~6Hz "
 
R is the headphone impedance in Ohms and C is the capacitor value in Farads (which is 0.00039390F aka 390uF in this amp).  
 
So for your 16 ohm IEMs...
F-3dB = 1 / 2Pi(16 ohms)(0.00039F) = ~26 Hz
 
If you'd rather cheat, here is an online calculator that does it for you...
 
-3dB at 26 Hz would be subtle but possibly audible, especially in the sub bass, at least.  Do you have any other cans to listen with?  I also may inquire at DIYA about using a larger output cap to pair better with sensitive headphones, although I'm not sure how big a cap will fit or whether if it may have any effect on sound quality in other ways.

 

The ALO CDM looks insanely nice...did you part ways with yours?  How hot did that thing get?

 

fascinating post, so much to learn. Thank you!

 

The CDM was lent to me by a good friend on the forums.  It's incredible.

 

I will review your post and come back with a more detailed response later, too late now to deciper that and I'm watching ufc!

 

Bass rolloff is fine and may be just what the bass excessive-treble rolled off A12 needs.  I'll be getting an Empire Ears XR ADEL in a bit to so I'll be able to use that with the AMP if I get to demo it.

 

Thanks again!

post #19 of 161
Thread Starter 

PCBs are in the mail!  I'm awaiting two.  Here's a sneak peak from the one that the designer, Xrk971, recently completed.

 

 

There has been some discussion on the DIYA thread about substituting different capacitors in this design.  I've decided on upgrading the power rail capacitors in my amps from 100uF Panasonic OSCONs to 1000uF Nichicon UKAs.  I'm told this will significantly lower crosstalk between channels.  For the output caps, I am going to upgrade from 390uF OSCON to a 1000uF OSCON.  This will lower the output impedance to provide deep bass extension with all headphones, including low impedance cans.  The treble frequencies are still handled by a 1uF WIMA film bypass caps, which I am not changing from the original design.  I am essentially stuffing my tins with the highest value capacitors that will possibly fit.  In order to accomplish this, I will have to mount the caps on their sides in this fashion and bend the leads a little funny, but it should work just fine and hopefully sound amazing.

Can't wait to get started!


Edited by stellarelephant - 2/24/17 at 8:08am
post #20 of 161
Thread Starter 

This amp is now available as a complete and tested board, for those not interested in soldering.  Xrk971 is now building them himself and offering them for sale on eBay, and all you have to do is put the finished PCB in a mint tin and hook up to 9v batteries.  Pocket Class A Headphone Amplifier 

 

 

Here are some highlights of this design he included in his listing:

 

  • Ultra-low -126dB noise floor
  • Tube-like harmonic distortion profile with only 0.028% THD (1kHz 700mV into 270 ohms) that is predominantly second harmonic (90%) 
  • Dynamic range of 94.2dB 
  • Stereo Cross-Talk of better than -74dB
  • Flat frequency response from 15Hz to 40khz (+/-0.5dB)

Edited by stellarelephant - 2/24/17 at 8:09am
post #21 of 161
Thread Starter 

My two boards arrived today!  :D

 

post #22 of 161
Quote:
Originally Posted by stellarelephant View Post
 

My two boards arrived today!  :D

 

 

i got mine too. i also have all the parts, hopefully i'll be able to build one of them this weekend.

post #23 of 161
Thread Starter 
Congrats, although I'm a bit jealous! I was busy and I only finally placed my Mouser and Digikey orders last night. I also picked up a new soldering iron off Amazon because I doubted my junky RadioShack iron would be up to the task of SMD work. Please keep us updated!
post #24 of 161

will sure do!

post #25 of 161
Hi guys. Glad the boards made it safely to you so quickly. Morde (Finland) has first sound already. He's fast.

Let me know if you have any questions with the build.

StellarElephant - your matched FETs were sent out yesterday you should have it soon.
post #26 of 161
Thread Starter 
Glad you're here, X!
post #27 of 161

Have you guys seen the new data I took from an electrically quieter room?  The noise floor is now -126dB and flat no peaks/bumps at 60Hz. The amp is super quiet, like it is not even turned on when music stops playing (even on my 112dB/mW balanced armature Aurvana 3 IEM's I can't tell it is on).

post #28 of 161
Thread Starter 

Awesome.  I figured that the noise at 60 Hz had to be from your home wiring since the amp is DC.  I own an EMF meter that is really fun to take around the house and "see" the fields generated by wall warts, fan motors, wiring, etc.  Definitely made me NOT want to put my bed near the breaker box.

 

I'll edit the specs I have posted here and in the portable amp forum, to reflect your new results.

post #29 of 161

A complete unit installed in the tin would be great...

 

Great little project anyway!

post #30 of 161
Quote:
Originally Posted by Lohb View Post

A complete unit installed in the tin would be great...

Great little project anyway!

If that's stopping you from ordering I could throw in the pre-drilled tin and Kapton heat transfer tape.
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